112 SULPHUR stirring. The precipitate is collected on a double filter, washed, dried, ignited and weighed as usual.1 BaS04 X 0-1374 = S. 2. Crude Sulphur. Crude sulphur is examined for the presence of bitumen, while the mois- ture and sulphur are detei mined. In order to obtain a representative sample, each of a, number of the loaves or lumps is 'broken into o'-8 parts and from each part a, slice cut from top to bottom, so that the proportions of sulphur, bitumen a.nd extraneous substances are maintained in each slice. This is of great importance, for loaves containing so-called oil or metal (veining or brown layers) or adul- terated with earthy matter. I'Vom 5 to 1,0 kilos are taken, pulverised and passed through a silk sieve, the coarser particles being re-ground and again sieved until the whole is in fine powder, which is thoroughly mixed. 1. Bitumen .---A little of the sample is heated in a tube and any car- bonaceous residue noted. Another way is to dissolve the .sample in carbon disulphide and allow the filtered liquid to evaporate spontaneously in a small crystallising dish. : in presence of bitumen, a, brownish or dark brown border forms on the walls of the vessel and when all the solvent vanishes, crystals of sulphur remain with brown tufts at. the salient points. 2. .Determination of the Moisture. -5 grams of the sample are healed in a tared porcelain dish at TOO" in a, steam-oven for r 2 hours (according to some, at: 70-80" for i hour), the loss representing moisture. 3. Determination of the Sulphur. The dried sulphur is next care- fully heated until the sulphur is completely evaporated, (he loss then giving the sulphur. If the sample contains bitumen, the sulphur must be deter- mined by the method described for mineral, sulphur. These methods may be applied directly to good sulphurs which leave only traces of residue on ignition, but where appreciable mineral residue remains, the residue from the carbon disulphide extraction is employed. 3, Refined Sulphur (loaves or powder) In re-fined sulphur in loaves or powder (ground, winnowed) the residue on calcination is determined to cheek the purity. Wilh sulphur ground and sifted for agricultural purposes, the degree of fineness must be deter- mined. Determination of the Degree of Fineness.-.....This is effected by Chancel's so-called S'ltlphurimclw or ^'ii'//>/iiinmc/c>', which consists of a, glass tube, with a, ground stopper : the tube is 230 mm. long and is graduated from o to too for a space corresponding exactly willi 45 c.c. at 17-5". The 1 To eliminate possible errors due to impurities in the reagents and to allow for the filter-ash, a blank determination may be carried out as follows : 25 e.e. uf the nitric acid (D =B 1-52) and 5 drops of bromine, diluted with a little water, are evaporated almost to dryness on a water-bath, the, whole of the nitric, acid being impelled by evaporating twice with cone, hydrochloric acid. The residue is taken up in water, a little barium chloride added and the liquid again evaporated almost to dryucss, filtered through a double filter, the latter washed with hot water, dried, ashed and weighed. The weight of this residue is subtracted from that of the barium sulphate obtained in the actual determination of the sulphur.ution = 0-005 gram Na2S.